Post by Deleted on Jan 23, 2013 1:20:55 GMT
History of DNA
Gregor Mendel – 1857 – Gregor showed dominant and recessive traits in DNA. He started with 34 peas and reproduced over 1,000 more peas. He observed that there were several traits of the peas that differed from the other peas.
Lawrence Bragg – 1912 to 1914 – Came up with Bragg’s law, which is one of the basic rules for crystal structure. This help led to the Franklin and Wilkins experiments.
Frederick Griffith – 1928 – He put pneumococcus bacteria into mice. The bacteria covered itself with polysaccharide capsule that would protect itself from the host’s immune system, causing the host to die. This was one of the first experiments that tested the transformation of bacteria.
Erwin Chargaff – 1940’s – He took samples of DNA and tested them to see the amounts of adenine, thymine, guanine and cytosine. The results turned up the adenine were equal to thymine and guanine was equal to cytosine. He also had 2 rules: %A = %T and %G = %C.
Oswald Avery – 1940’s – Oswald Avery destroyed the lipids, carbohydrates, ribonucleic acids, and proteins of pneumonia. The bacteria still went through transformation. He did the same thing again, but with deoxyribonucleic acid. The bacteria did not transform. Avery had founded DNA.
Franklin and Wilkins -1950’s - Rosalind Franklin and Maurice Wilkins made a crystal of a DNA molecule. They did this because if they could get the DNA crystalized, they could take x-rays of the DNA and it would show them how DNA worked. This test was successfully done. The x-rays showed rungs (like a ladder) and a X shape.
Messelshon and Stahl - 1950’s - Their experiment showed correctness of the semiconservative model of DNA replication. They grew bacteria in 14N or 15N medium until the samples were removed. They then extracted the DNA from the bacteria. It showed two bands of DNA with 2 different densities.
Alfred Hershey and Martha Chase - 1952 – These 2 researchers concluded that DNA is where life's hereditary data is found. They took nuclei of bacteriophages and took the protein case on it off in the blender. They injected nucleic acid into the bacterial celll, and it turned into an acid that caused the transformation of genetic material.
James Watson and Francis Crick – 1953 – They successfully made a model of a DNA molecule. They took the purines and pyridines and made the pairs the rungs. This made the molecule look wrong so they changed it to thymine and adenine or guanine and cytosine. There would also be a hydrogen bond formed between the two base pairs.
-Brandon Lynd